Method for gumming a reconstituted tobacco leaf

ABSTRACT

The present invention relates to a reconstituted tobacco leaf coated with a stripe of adhesive along one of its margins, the linear mass of the stripe of adhesive being greater than 70 mg/m in the dry state. The invention also provides a method of depositing such a stripe, and apparatus for depositing such a stripe of adhesive.

The present invention relates to the field of smokers' articles.

More precisely the invention relates to the field of such articles usingat least one reconstituted tobacco leaf.

Proposals are made in French patent application FR-97/15845 in the nameof the Applicant, for an article enabling consumers to prepare their owncigarillos, said article comprising in particular a set of reconstitutedtobacco leaves that are interleaved in such a manner as to enable themto be dispensed automatically by pulling on the various leaves insuccession.

In such an article, each reconstituted tobacco leaf, also referred to asa “tobacco leaf” has a stripe of adhesive applied to one of its margins.Once the stripe of adhesive has dried, the leaves are interleaved.

The stripe of adhesive makes it possible, once a leaf has been rolledup, to stick down its margin on the roll formed in this way. Theadhesives used for this purpose include, in particular, food gradeadhesives enabling the user to stick down the margin with the help ofsaliva.

With leaves that have been coated with a stripe of food grade adhesive,the adhesive used can either be a cold adhesive deposited at ambienttemperature and dried by convection, or a hot adhesive, e.g. a naturalgum arabic or a synthetic adhesive that is deposited while hot and isdried by radiation (of the infrared type) that is localized in registerwith the stripe of adhesive, or else is dried in a convective oven.

The techniques presently used for putting such stripes of adhesive intoplace are not satisfactory.

In particular, it turns out that the tobacco leaf absorbs the gum tosuch an extent that the leaf with its stripe of gum has adhesiveproperties that are poor.

Previously proposed leaves with their stripes of adhesive enable onlyparticularly fragile cigarillos to be made.

A main object of the invention is to propose a reconstituted tobaccoleaf where the stripe of adhesive lining one of its margins enables saidmargin to be secured in satisfactory manner to the remainder of theleaf.

In the context of the present invention, this object is achieved by areconstituted tobacco leaf coated with a stripe of adhesive along one ofits margins, the leaf being characterized in that the linear mass of thestripe of adhesive in the dry state is greater than 70 milligrams permeter (mg/m).

In another aspect, the invention provides a method of applying such astripe of adhesive on a reconstituted tobacco leaf, whereby the tobaccoleaf conserves a certain amount of elasticity after the stripe ofadhesive has been put into place. In known methods for applying a stripeof adhesive, the stripe of adhesive is dried in a manner that also leadsto the leaf drying and thus becoming brittle. The leaf loses so muchstrength that it becomes practically impossible to use the leaf to makea smokers' article in which it needs to be tightly curved.

A method of the invention for applying a stripe of adhesive is a methodin which the adhesive is dried by heating the leaf carrying the stripe,and in which the moisture content of the leaf is maintained duringdrying at greater than 7%.

In a third aspect of the invention, an apparatus is provided forimplementing such a method, the apparatus consisting in an oven providedwith means for moving the leaves in translation, said means passingthrough the oven, and having means for spraying water on entry into theoven and at least one air-blowing nozzle which is disposed so as to blowair on the stripe of adhesive.

Other characteristics, objects, and advantages of the present inventionwill appear on reading the following detailed description.

The gums that have been proposed in the past for tobacco leaves aresubstantially the same as those used on conventional cigarette paper.Unfortunately, those gums have been found to be difficult to use in thisparticular application since they adhere particularly weakly to tobaccoleaves.

In addition, it is conventional to deposit a stripe of gum on a tobaccoleaf with a linear mass of gum lying in the range about 40 mg/m to 50mg/m, where such a quantity of adhesive is considered as being aparticularly high quantity.

In order to dry such a quantity of adhesive, it is already necessary tosubject the leaves to heating that makes them particularly brittle.

A reconstituted tobacco leaf is particularly sensitive to variations inmoisture content, and in particular, when gum is applied thereto, dryingthe gum by means of heat causes the moisture content of thereconstituted tobacco to drop from 14% to about 4%, which has the effectof making the leaf brittle to such an extent that it is no longerpossible, in practice, to handle it without leading to a large number ofbreaks.

In addition, if the amount of drying applied to the leaf is reduced,then a first effect is that the gum is dried incompletely, even thoughthe leaf is still made most inconveniently brittle.

The fact of the gum being incompletely dried gives rise to untimelysticking while the leaf is being rolled up, or during subsequenthandling thereof, with this problem being in addition to the leaf beingbrittle. In particular, it then becomes practically impossible toperform an interleaving operation.

Starting from this situation, the person skilled in the art ofreconstituted tobacco leaves has not attempted to increase the quantityof adhesive in the stripe, since any such increase, even if only veryslight, has been perceived as giving rise only to disadvantages.

Surprisingly, the inventors have found that when the linear mass of thestripe of adhesive in the dry state exceeds about 70 mg/m, then itpresents adhesive properties that are particularly effective, and with aquantity of adhesive greater than that it is possible to make a drystripe without causing the leaf to become unusually brittle duringdrying.

In preferred manner, in terms of mechanical strength, the tobacco leafis provided with a stripe of gum whose linear weight lies in the range80 mg/m to 100 mg/m in the dry state, with a strength and an ease ofimplementation effect that is particularly surprising in the range 90mg/m to 95 mg/m in the dry state. The term “mass in the dry state” meansthe mass of adhesive after drying, or the mass of dry extract ofadhesive.

To produce satisfactory drying of such a stripe while avoiding thepreviously observed effect of the leaf becoming brittle, the stripe isdried in an oven provided with strips for spraying demineralized waterinside the oven. In the embodiment described herein, the stripe ofadhesive is deposited immediately before the reconstituted tobacco leafenters the oven.

In this case, the oven is a convective oven provided with means fordriving the leaves that pass through it. The length of the oven lies inthe range about 10 meters (m) to 15 m. It is provided with an inletspray strip and with a spray strip located substantially in the middleof the oven.

These spray strips enable the leaf to be maintained sufficiently moistthroughout the operation of gumming and in particular of drying.

Thus, during those operations taken together, and in particular duringtreatment in the oven, the leaf is maintained so that its moisturecontent lies in the range 12% to 14%.

With moisture content being maintained in this range, the gummed leaf atthe outlet from the oven has moisture content of about 8% to 10%.

These moisture conditions have been identified as being optimal in termsof enabling the leaf to be handled subsequently without excessive lossof tobacco leaf due to breaking.

More generally, in accordance with the invention, care is taken tomaintain the leaf at adequate moisture content during the gummingoperation, and preferably at moisture content greater than 7%.

One or more strips for delivering compressed air are located at theoutlet from the oven to form nozzles that are directed onto the stripesof gum.

These arrangements are particularly effective in drying the gum withoutdrying the leaf, and in particular in drying any excess gum.

In conventional manner, the ovens used for drying the gum placed on thetobacco leaves are maintained at a temperature lying in the range 120°C. to 140° C.

Likewise in conventional manner, the gum is deposited on the leaf andthe leaf is transported through the oven during drying at a “gumming”speed which lies in the range 60 meters per minute (m/min) to 80 m/min.

The inventors have been able to determine an oven temperature that isparticularly suitable for effective drying of the gum while enabling themoisture content of the tobacco leaf to be maintained within theabove-specified ranges.

Thus, in accordance with the invention, an oven temperature is used thatis selected to lie approximately in the range 70° C. to 90° C., and agumming speed is selected that lies approximately in the range 18 m/minto 20 m/min. For the 15 m oven used in this case, this travel speedcorresponds to an optimum drying time under heating of about 45 seconds(s). More generally, the ideal drying time lies in the range 30 s to 1min.

By means of these dispositions, the resulting gummed tobacco leaf at theoutlet from the oven presents moisture content lying in the range 8% to10% and it has a stripe of gum that is completely dry.

These conditions are optimal for moving on to the interleaving operationwhen a dispenser is provided having interleaved leaves.

Naturally, these conditions are described with reference to a convectiveoven, however it would also be possible to adapt them for use in aradiant oven. Under such circumstances, an oven should be used having alength of approximately 2 m to 4 m.

In the present method, on leaving the oven, the tobacco leaf is storedon bobbins. The bobbins are then protected from evaporation by beingwrapped in an impermeable plastics film or in any other leakproofcovering.

Preferably, and in accordance with the invention, the moisture contentof the tobacco leaf is also controlled during the interleavingoperation.

For this purpose, strips for spraying demineralized water are installedat the inlet to apparatus for performing interleaving.

Naturally, the above-described dispositions are not limited to making asmokers' article having interleaved leaves.

The tobacco leaf and the methods described herein can be applied tomaking any other smokers' article within the ambit of the invention.

What is claimed is:
 1. A reconstituted tobacco leaf coated with a stripeof adhesive along one of its margins, the leaf being characterized inthat the linear mass of the stripe of adhesive in the dry state isgreater than 70 mg/m.
 2. A reconstituted tobacco leaf according to claim1, characterized in that the linear mass of the stripe of adhesive inthe dry state is greater than 80 mg/m.
 3. A reconstituted tobacco leafaccording to claim 1 or 2, characterized in that the linear mass of thestripe of adhesive in the dry state is greater than 90 mg/m.
 4. Areconstituted tobacco leaf according to claim 1 or 2, characterized inthat the linear mass of the stripe of adhesive in the dry state lies inthe range 90 mg/m and about 95 mg/m.
 5. A method of applying a stripe ofadhesive along a margin of a reconstituted tobacco leaf characterized inthat the stripe is applied in such a quantity that the linear mass ofthe stripe of adhesive in the dry state is greater than 70 mg/m.
 6. Amethod according to claim 5, further comprising drying the leaf whereinthe moisture content of the leaf is maintained during the drying in therange 12% to 14%.
 7. The method of claim 5, characterized in that theadhesive is dried by heating the leaf provided with the stripe ofadhesive, and in that the moisture content of the leaf is maintainedduring drying at more than 7%.
 8. A method according to any one of claim5, 6 or 7 characterized in that the stripe of adhesive is deposited onthe leaf at a deposition speed of about 18 meters per minute to 20meters per minute.
 9. The method according to claim 5, 6 or 7characterized in that the method is carried out with an oven which isprovided with means for moving the reconstituted tobacco leaves thatpass through the oven in translation, means for spraying water at theentrance to the oven, and at least one nozzle blowing air that islocated to blow on the stripe of adhesive.
 10. A method according toclaim 6 or 7, characterized in that the duration of drying lies in therange 30 seconds to 1 minute.
 11. A method according to any one of claim6 or 7 characterized in that drying is performed by drying the leaf inan oven, and in that moisture content is maintained by spraying waterinside the oven.
 12. A method according to claim 11, characterized inthat the temperature of the oven is selected to lie in the range ofapproximately 70° to 90° C.
 13. A method according to any one of claim 6or 7 characterized in that compressed air is blown onto the stripe ofadhesive during drying.
 14. A method of making a smokers' articlecomprising a set of reconstituted tobacco leaves, the leaves beinginterleaved so as to enable them to be dispensed automatically bypulling on the various leaves in succession, the article comprising acontainer-dispenser suitable for receiving said set of interleavedleaves and for controlling the dispensing thereof, the method beingcharacterized in that a stripe of adhesive is applied along a margin ofeach tobacco leaf before the leaves are interleaved, in such a quantitythat the linear mass of each stripe is greater then 70 mg/m.
 15. Amethod according to claim 14 further comprising drying the leaves,characterized in that the leaves are maintained in a leakproof coveringbetween an end of the drying and a beginning of the interleaving. 16.The method of claim 14 characterized in that water is sprayed on a leafprior to interleaving the leaf with the other leaves.